1. Field of the Invention
The present invention mainly relates to a winding method of a low-profile spiral coil for a magnetic head used in, e.g., a magnetooptical recording apparatus which adopts a magnetic field modulation system.
2. Related Background Art
A magnetic field modulation system is known as a magnetooptical recording apparatus for recording information at high density on a magnetooptical recording medium such as a magnetooptical disk. In this system, a laser beam is converged to a spot size of about 5 .mu.m, and is radiated onto a recording medium. At the same time, a magnetic head applies a magnetic field modulated in accordance with an information signal onto the portion irradiated with the laser beam, thereby recording the information signal.
In a conventional magnetooptical recording apparatus of the magnetic field modulation system, a magnetic head having an arrangement shown in FIG. 1 is used. Referring to FIG. 1, the magnetic head comprises a magnetic member 6 consisting of a magnetic material such as Mn-Zn ferrite having a high magnetic permeability, and a coil 7 constituted by winding a conductive wire (magnet wire) with an insulating coat, which wire has a diameter of 40 to 70 .mu.m, around the magnetic pole of the magnetic member 6.
In recent years, in order to meet a requirement for a high information signal recording speed, the frequency of a recording signal tends to be set to be high. When a magnetic field is modulated at such a high frequency, the magnetic head is required to have characteristics including a low inductance and a low high-frequency resistance.
Thus, the present inventor has already proposed a magnetic head in which a coil obtained by two-dimensionally winding a magnet wire is mounted onto a substrate consisting of a magnetic material, as a head which has good productivity in addition to desired characteristics including a low inductance and low high-frequency resistance (Japanese Laid-Open Patent Application No. 4-181507).
FIG. 2 is a perspective view of such a magnetic head. The magnetic head comprises a substrate 8 consisting of a magnetic material such as Mn-Zn ferrite having a high magnetic permeability, and a magnetic pole 9 also consisting of a magnetic material such as Mn-Zn ferrite having a high magnetic permeability. Note that a coil 10 is constituted by two-dimensionally winding a magnet wire around the magnetic pole 9. A groove 8a extending outwardly from the winding center of the coil 10 is formed on the substrate 8, and receives a lead wire portion 10a of the coil, so that the lead wire is led outside the magnetic head. As described above, since the coil is two-dimensionally wound, the inductance and the high-frequency resistance of the magnetic head can be sufficiently lowered. Also, since the lead wire portion of the coil is stored in the groove formed not on the upper surface of the coil but on the substrate, and is led outside the magnetic head, the coil can be set sufficiently close to a recording medium. For this reason, high magnetic field generation efficiency can be obtained.
As described above, in the conventional magnetic head, since the lead wire portion of the coil is stored in the groove formed on the substrate, and is led outside the magnetic head, the coil can be realized by two-dimensionally winding the magnet wire around the magnetic pole. However, since this magnetic head requires a process of forming the groove on the substrate, and also requires a process of storing the lead wire portion of the coil in the groove, sufficiently good productivity cannot be obtained yet. In particular, when a magnet wire having a smaller wire diameter is used to efficiently generate a magnetic field, the above-mentioned groove formation process, lead wire storage process, and the like become more difficult.